Abstract:The switching of electric polarization
induced by electric fields,
a fundamental functionality of ferroelectrics, is closely associated
with the motions of the domain walls that separate regions with distinct
polarization directions. Therefore, understanding domain-walls dynamics
is of essential importance for advancing ferroelectric applications.
In this Letter, we show that the topology of the multidomain structure
can have an intrinsic impact on the degree of switchable polarization.
Using a combination of … Show more
“…These thermodynamically stable domains may not be easily switched under an applied electric field and thus the macroscopic remanent polarization can be reduced as compared to the single domain state. 18 The distinct feature of our b-glycine microcrystals is a presence of a large number of charged domain walls (either head-to-head or tail-to-tail). In uniaxial ferroelectrics, 180 domain walls typically separate antiparallel domains with polarization vector parallel to domain plane, so as to avoid high electrostatic energy associated with polarization discontinuity at the domain wall.…”
Section: Resultsmentioning
confidence: 97%
“…The combination of both represents a typical step-like domain structure similar to that recently observed in a-6,6 0 -dimethyl-2,2 0 -bipiridinium chloranilate. 18 Figure 2 shows a part of the step-like domain structure overlaid on the 3D topography image. It clearly indicates that the 180 domains are mostly coincident with the cleavage planes of the crystal.…”
Section: Resultsmentioning
confidence: 99%
“…19 Consequently, charged domain walls have been rarely observed in ferroelectric materials, e.g., in PbTiO 3 crystals, 20 in PZT thin films 21 and, recently, in uniaxial organic ferroelectrics. 18 An as-grown glycine crystal has both antiparallel (neutral) and charged ferroelectric domain walls appearing as a series of steps as shown schematically in Fig. 3.…”
Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and a switchable polarization at room temperature. Here, we study tip-induced domain structures and polarization switching in the smallest amino acid b-glycine, representing a broad class of non-centrosymmetric amino acids. We show that b-glycine is indeed a roomtemperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of an applied voltage and pulse duration. The domain shape is dictated by polarization screening at the domain boundaries and mediated by growth defects. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that the properties of b-glycine are controlled by the charged domain walls which in turn can be manipulated by an external bias. V C 2015 AIP Publishing LLC. [http://dx
“…These thermodynamically stable domains may not be easily switched under an applied electric field and thus the macroscopic remanent polarization can be reduced as compared to the single domain state. 18 The distinct feature of our b-glycine microcrystals is a presence of a large number of charged domain walls (either head-to-head or tail-to-tail). In uniaxial ferroelectrics, 180 domain walls typically separate antiparallel domains with polarization vector parallel to domain plane, so as to avoid high electrostatic energy associated with polarization discontinuity at the domain wall.…”
Section: Resultsmentioning
confidence: 97%
“…The combination of both represents a typical step-like domain structure similar to that recently observed in a-6,6 0 -dimethyl-2,2 0 -bipiridinium chloranilate. 18 Figure 2 shows a part of the step-like domain structure overlaid on the 3D topography image. It clearly indicates that the 180 domains are mostly coincident with the cleavage planes of the crystal.…”
Section: Resultsmentioning
confidence: 99%
“…19 Consequently, charged domain walls have been rarely observed in ferroelectric materials, e.g., in PbTiO 3 crystals, 20 in PZT thin films 21 and, recently, in uniaxial organic ferroelectrics. 18 An as-grown glycine crystal has both antiparallel (neutral) and charged ferroelectric domain walls appearing as a series of steps as shown schematically in Fig. 3.…”
Bioorganic ferroelectrics and piezoelectrics are becoming increasingly important in view of their intrinsic compatibility with biological environment and biofunctionality combined with strong piezoelectric effect and a switchable polarization at room temperature. Here, we study tip-induced domain structures and polarization switching in the smallest amino acid b-glycine, representing a broad class of non-centrosymmetric amino acids. We show that b-glycine is indeed a roomtemperature ferroelectric and polarization can be switched by applying a bias to non-polar cuts via a conducting tip of atomic force microscope (AFM). Dynamics of these in-plane domains is studied as a function of an applied voltage and pulse duration. The domain shape is dictated by polarization screening at the domain boundaries and mediated by growth defects. Thermodynamic theory is applied to explain the domain propagation induced by the AFM tip. Our findings suggest that the properties of b-glycine are controlled by the charged domain walls which in turn can be manipulated by an external bias. V C 2015 AIP Publishing LLC. [http://dx
“…In our case, application of an external (coplanar) electric field removes the charged domain walls; however, the compensating charges (in the bulk) still reside at the same locations as before usually at the grain boundaries (see the inset in Fig. 5), and therefore produce large internal fields, 32 triggering the relaxation of the electrically induced single-domain-states back to the as-grown domain state. Moreover, the observed relaxation is likely aided by incomplete screening of polarization at the coplanar metal electrodes because of poorly defined metal/ferroelectric interface and non-uniform film coverage.…”
mentioning
confidence: 78%
“…For charged domain walls to exist, the bound charges in the bulk associated with discontinuity of polarization should be effectively screened by the mobile charges and/or immobile charged defects. Recent observations 27,32 suggest the existence of stable as-grown charged (head-to-head and tail-to-tail) domain wall configurations in organic ferroelectrics with origin of compensating screening charges yet to be understood. In our case, application of an external (coplanar) electric field removes the charged domain walls; however, the compensating charges (in the bulk) still reside at the same locations as before usually at the grain boundaries (see the inset in Fig.…”
Switching characteristics of vinylidene fluoride oligomer thin films with molecular chains aligned normal to the substrate and exhibiting a preferential in-plane polarization have been investigated using coplanar geometry of inter-digital electrodes via high-resolution piezoresponse force microscopy. It has been shown that in-plane switching proceeds via non-180° rotation of dipoles mediated by non-stochastic nucleation, expansion, and coalescence of domains. As-grown multidomain configuration is found to be strongly pinned aided by charged domain walls, and the electrically induced (in-plane) mono-domain states relax to the as-grown state. The observed coercive field (approximately 0.6 MV/m) is two to three orders of magnitude smaller than that for the oligomer films with out-of-plane polarization. It is suggested that the low steric hindrance to the rotation of molecular dipoles gives rise to the observed low coercive field.
Application of scanning probe microscopy techniques such as piezoresponse force microscopy (PFM) opens the possibility to re-visit the ferroelectrics previously studied by the macroscopic electrical testing methods and establish a link between their local nanoscale characteristics and integral response. The nanoscale PFM studies and phase field modeling of the static and dynamic behavior of the domain structure in the well-known ferroelectric material lead germanate, Pb 5 Ge 3 O 11 , are reported. Several unusual phenomena are revealed: 1) domain formation during the paraelectric-to-ferroelectric phase transition, which exhibits an atypical cooling rate dependence; 2) unexpected electrically induced formation of the oblate domains due to the preferential domain walls motion in the directions perpendicular to the polar axis, contrary to the typical domain growth behavior observed so far; 3) absence of the bound charges at the 180° head-to-head (H-H) and tail-totail (T-T) domain walls, which typically exhibit a significant charge density in other ferroelectrics due to the polarization discontinuity. This strikingly different behavior is rationalized by the phase field modeling of the dynamics of uncharged H-H and T-T domain walls. The results provide a new insight into the emergent physics of the ferroelectric domain boundaries, revealing unusual properties not exhibited by conventional Isingtype walls.
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